Footage shows the young primate repeatedly punches the tiny creature and then casually throws its lifeless body around its enclosure.
A small child is heard shouting 'what is he doing' as the animal pounds its victim with its bare hands.
The horrifying incident took place on May 19 at Taronga Zoo in Sydney, Australia.
Staff said they were not able to intervene in the assault, according to the person who filmed the video.
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He said: 'We walked up to the chimpanzees only to see seven ducklings being beaten to death.
''I turned around to the Taronga Worker and said 'can't you get these ducklings out?' only for her to respond: 'Unfortunately they aren't part of our exhibit'.''
